The study proposed is directed toward the elucidation of mechanisms involved in the effective immunity to schistosomiasis, with emphasis on Schistosoma japonicum. Investigation of immediate and delayed hypersensitivity in humans infected with S. japonicum and correlative studies in animals experimentally infected with S. japonicum and other schistosomes are being carried out. These include the investigation of anti-DNA antibody in infected hosts, circulating DNA and antigen- antibody complexes and the possible autoimmune or immune complex renal damage in schistosome infection. Studies of host immune tolerance to the schistosome and its antigens are being continued as are in vitro culture studies effects of immune sera from man and experimentally infected animals on schistosomules. The degree of delayed hypersensitivity response is also being studied using blast transformation techniques.